This invention relates to the field of cryogenic liquids. In particular, the invention provides an apparatus and method for adding droplets of a cryogenic liquid to cans or plastic bottles, such as beverage containers. However, the invention can be used in any other application requiring the controlled dispensing of droplets of a cryogenic liquid.
Beverage containers made of aluminum or plastic have the advantage of being light in weight and relatively low in cost. But the softness of these materials makes it impractical to stack aluminum or plastic containers, unless the containers are pressurized, as would be true for carbonated beverages. Thus, to overcome the problem for the case of non-carbonated beverages, it has been known to inject small amounts of a cryogenic liquid, usually liquid nitrogen, into the container, immediately before the container is sealed. The cryogenic liquid vaporizes almost instantly, and expands to many times its original volume. The vaporized cryogen provides the desired internal pressure for the container.
U.S. Pat. Nos. 4,561,258 and 4,592,205, the disclosures of which are incorporated by reference herein, both show systems intended to deliver steady streams of cryogenic liquids, such as liquid nitrogen, for the purposes described above. U.S. Pat. No. 5,385,025, the disclosure of which is also incorporated by reference herein, shows a device which dispenses discrete droplets of cryogenic liquid into a container.
One of the problems with the devices of the prior art is that it is difficult to adapt the droplet dispensing equipment for use with nozzles of different sizes. In a typical injector of the prior art, the nozzle is an integral part of the vessel which holds the cryogenic liquid before it is dispensed. The vessel storing the cryogenic liquid typically has a portion of narrowing diameter that comprises the injector nozzle. Because the injector is thus an integral part of the vessel, it can be very difficult or impossible to vary the size of the nozzle. If the the nozzle size can be varied, one can use the same apparatus to work with containers of different sizes.
Another problem with the devices of the prior art is that such devices are not compact. It is often difficult to adapt a given piece of equipment for use in a small space, or to work with a particular carousel which holds a plurality of containers.
The handling of cryogenic liquids inevitably involves heat losses; some liquid becomes vaporized and escapes without being used. Such losses decrease the overall efficiency of the system, and increase the cost of operation. It is therefore desirable to improve the efficiency of prior art devices, by reducing unwanted losses of gas, and by providing a use for the gas that does escape from the reservoir of cryogenic liquid.
Another problem encountered in the operation of a liquid nitrogen injector is the tendency to form moisture and/or to cause icing. Icing and condensation are likely to form where the air is moist and cold, and such conditions are likely to occur in the presence of vaporized liquid nitrogen. Moisture can find its way to the delicate circuitry in the process control unit, eventually leading to deterioration of that circuitry. Icing is especially problematic when it forms at or near the nozzle. Ice can render the nozzle inoperative, blocking all flow of cryogenic liquid. In such cases, it is necessary to interrupt production, and either to replace the nozzle or de-ice it. Ice can also break off from the nozzle, and/or from the nozzle jacket, and can fall into the containers, in which case the containers are considered contaminated and unsalable. It is therefore essential to prevent ice from forming anywhere near the containers.
The present invention provides an apparatus and method which addresses the problems discussed above, and which provides an economical and effective solution to the problem of injecting a cryogenic liquid into containers.
The apparatus of the present invention includes a vessel for storing a cryogenic liquid, which can be liquid nitrogen. A flexible, thermally-insulated hose connects the vessel to a nozzle. A vertically oriented support holds the vessel at a desired level above the ground, and an adjustable arm, mounted to the support, holds the nozzle. The arm is mounted to the support such that the arm can move with two degrees of freedom, relative to the support. Also, the arm is preferably of telescopic construction, providing a third degree of freedom. Thus, due to the flexible hose and the construction and mounting of the arm, the position of the nozzle can be continuously varied, with three degrees of freedom, and the nozzle can thus be positioned virtually anywhere, within the limits defined by the length of the arm and the height of the support.
The apparatus is operated by a process control unit, which contains known circuitry for determining the timing of the dispensing of liquid nitrogen. Such circuitry also receives an input from one or more sensors located at or near a carousel of containers, so that the dispensing of liquid nitrogen can be properly coordinated with the position of each container. In the preferred embodiment, a fluid conduit, connected between the vessel and the process control unit, conveys vaporized nitrogen into the process control unit. The nitrogen vapor so used tends to purge the interior of the process control unit, and keeps it dry, thereby reducing the likelihood of moisture-induced deterioration of the circuitry.
Excess vaporized nitrogen, beyond that which is needed to purge the process control unit, is conducted through a channel in the support, and vented to the outside environment. The channel can be an integral part of the support, or it can be formed separately from the support but mounted within and/or along the support.
The nozzle of the present invention preferably includes a control gas port and a purge gas port. These ports are connected, by conduits, to a vaporizer, which is in turn connected to a source of cryogenic liquid. The latter source may be the same source that supplies the vessel. The purpose of the vaporizer is to provide a gas which can be used to control the formation of droplets in the nozzle, and/or to de-ice the nozzle. The nozzle includes a narrow neck portion, into which unheated gas is injected, through the control gas port, at low pressure, to control the formation of droplets. If the nozzle becomes iced, the gas entering the control gas port can be heated and injected at high pressure. The nozzle also includes a shroud which is connected to the purge gas port. A small amount of heated gas, at low pressure, is injected through the purge gas port, to prevent formation of ice in the shroud. If the shroud area becomes seriously iced, heated gas at high pressure can be injected through this port.
One or more orifices in the nozzle can be detached from the assembly, simply by loosening a few screws. In particular, the size of the droplets can be changed by removing and replacing the lower orifice, i.e. the orifice closest to the outlet of the nozzle.
The present invention also comprises a method of injecting a cryogenic liquid, such as liquid nitrogen, into containers. The method comprises selecting a nozzle and/or orifice according to the containers into which the cryogenic liquid is to be injected, connecting the nozzle to a flexible hose, positioning the nozzle with a movable arm connected to a support, and controlling the delivery of cryogenic liquid to the nozzle. The method also includes tapping at least some of the vaporized cryogenic liquid for use in purging a housing for a process control unit, so as to keep the contents of that housing dry. The method also includes providing a gas, formed by vaporizing a cryogenic liquid, the gas being used for controlling the formation of droplets and for preventing ice formation or for removal of ice.
The present invention therefore has the primary object of providing an apparatus for injecting a cryogenic liquid into a container.
The invention has the further object of providing a cryogenic liquid injector which easily accommodates injector nozzles or nozzle orifices of varying sizes.
The invention has the further object of providing a cryogenic liquid injector, in which the position of a nozzle can be continuously varied and controlled.
The invention has the further object of providing a cryogenic liquid injector which is compact.
The invention has the further object of improving the efficiency of a cryogenic liquid injector.
The invention has the further object of prolonging the life of a process controller used in conjunction with a cryogenic liquid injector.
The invention has the further object of providing a method of injecting a cryogenic liquid into containers.
The invention has the further object of providing a method and apparatus for injecting heated gas into a nozzle so as to de-ice that nozzle, or to prevent the formation of ice.
The invention has the further object of providing a de-icing method and apparatus as described above, wherein a minimum amount of gas is used for de-icing, and wherein the de-icing nevertheless proceeds rapidly.
The invention has the further object of providing a method and apparatus for dispensing a cryogenic liquid, wherein energy losses are minimized.
The invention has the further object of reducing the risk of contamination of beverage containers due to ice falling into the containers before they are sealed.
The reader skilled in the art will recognize other objects and advantages of the present invention, from the following brief description of the drawings, the detailed description of the invention, and the appended claims.